Florid Lobular Carcinoma In Situ (F-LCIS) Showing Predominantly Hypoechoic Masses With Obscured Margins and No Attenuated Posterior Echoes on Ultrasound: A Case Report.

Florid lobular carcinoma in situ (F-LCIS) is a rare disorder and has no established image findings to date. A 63-year-old woman was referred to our hospital for the detailed examination of the abnormality on screening mammography. Mammography showed a focal asymmetric density in the left breast. Ultrasound showed multiple round/oval masses with obscured margins, predominant low internal echoes, and no attenuated posterior echoes. MRI of the masses showed low signals on T1-weighted images, high signals on fat-suppressed T2-weighted images, fast enhancement followed by a washout pattern, and presumed ductal spread to the nipple base on dynamic studies. After the pathological diagnosis of predominant LCIS on core needle biopsy, the patient underwent nipple-sparing mastectomy and sentinel node biopsy followed by immediate breast reconstruction using the extended latissimus dorsi musculocutaneous flap. Postoperative pathological study showed that all four masses, except for the largest one, were F-LCIS, and the largest mass, 9 mm in pathological size, was predominant florid ductal carcinoma in situ (F-DCIS) with invasive components. The patient recovered uneventfully, was discharged on the 13th day after surgery, has been well for four months on adjuvant letrozole therapy, and is scheduled for long-term follow-up on an outpatient basis. Diagnostic physicians should note that predominantly hypoechoic masses with obscured margins and no attenuated posterior echoes may be important ultrasound findings of F-LCIS.